Milton Zysman, when discussing extinction events, said that around 30,000 years ago (please note modern calculations are anything between 40,000 and 30,000 years ago) the Earth reversed its magnetic field. This, he claimed, coincided with the appearance of modern humans and the disappearance of the Neanderthals (in western Asia and Europe). He suggested that electrical exchanges between the Earth and a passing comet was involved in the reversal event. It may even have toppled the axis of rotation, he said, re-establishing itself in an inverted position. In the general melee that followed the Neanderthals died out.